Re: [PATCH v5 20/37] mm: fix non-compound multi-order memory accounting in __free_pages

[Vlastimil Babka]

On 3/6/24 19:24, Suren Baghdasaryan wrote:
> When a non-compound multi-order page is freed, it is possible that a
> speculative reference keeps the page pinned. In this case we free all
> pages except for the first page, which will be freed later by the last
> put_page(). However put_page() ignores the order of the page being freed,
> treating it as a 0-order page. This creates a memory accounting imbalance
> because the pages freed in __free_pages() do not have their own alloc_tag
> and their memory was accounted to the first page. To fix this the first
> page should adjust its allocation size counter when "tail" pages are freed.
> 
> Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>

Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>